Known door and window contacts utilized in intrusion detection systems are typically based on reed and magnet technology. This technology, although inexpensive to implement, has limitations. The two major ones are gap limitations and security vulnerability.
“Wide-gap” reed switch contacts have had their maximum functional gaps stretched to reliable limits through various methods. However, mounting on surfaces constructed of ferrous materials results in a magnetic flux field interference that further reduces the maximum operating gap.
Most reed based contacts are also defeated by the use of a magnet introduced in close proximity to the reed by an intruder. There are numerous improved implementations that reduce this security vulnerability, but with additional cost. The challenge is to significantly overcome these issues without increasing the cost of the end product.